Common carrier has worked out for other utilities in the past. Publicly owned infrastructure is the next step.

You can view it as simply as, developing a single distribution network and subscribing to Comcast/AT&T/etc at your discretion over that common distribution network saves everyone money, because the city has only one distribution network rather than several cable networks, DSL, satellite, etc. It additionally could encourage competition among service providers, as incumbents would not need to develop their own distribution network.